소개

Request로 들어온 데이터는 Filter, Interceptor에서 사용하게 되면,
그 이후 사용이 불가능하므로 Caching 할 수 있는 Wrapper를 새로 만들기 위한 코드다.

소스 코드

MultiReadRequestWrapper

java
public class MultiReadRequestWrapper extends HttpServletRequestWrapper {
    private byte[] cachedBody;

    public MultiReadRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        // 생성 시점에 바디를 미리 읽어서 보관합니다.
        InputStream is = request.getInputStream();
        this.cachedBody = StreamUtils.copyToByteArray(is);
    }

    @Override
    public ServletInputStream getInputStream() {
        // 호출될 때마다 보관된 바이트 배열로 새 스트림을 만듭니다.
        ByteArrayInputStream bais = new ByteArrayInputStream(this.cachedBody);
        return new ServletInputStream() {
            @Override
            public int read() {
                return bais.read();
            }

            @Override
            public boolean isFinished() {
                return bais.available() == 0;
            }

            @Override
            public boolean isReady() {
                return true;
            }

            @Override
            public void setReadListener(ReadListener readListener) {
            }
        };
    }

    @Override
    public BufferedReader getReader() {
        return new BufferedReader(new InputStreamReader(this.getInputStream()));
    }

    // 캐싱된 응답 바디를 꺼내보는 메서드
    public byte[] getContentAsByteArray() throws IOException {
        return StreamUtils.copyToByteArray(getInputStream());
    }
}

MultiReadResponseWrapper

java
public class MultiReadResponseWrapper extends HttpServletResponseWrapper {
    private final ByteArrayOutputStream capture = new ByteArrayOutputStream();
    private ServletOutputStream output;
    private PrintWriter writer;

    public MultiReadResponseWrapper(HttpServletResponse response) {
        super(response);
    }

    @Override
    public ServletOutputStream getOutputStream() {
        if (writer != null) throw new IllegalStateException("Writer already in use");
        if (output == null) {
            output = new ServletOutputStream() {
                @Override
                public void write(int b) { capture.write(b); }
                @Override
                public void setWriteListener(WriteListener writeListener) {}
                @Override
                public boolean isReady() { return true; }
            };
        }
        return output;
    }

    @Override
    public PrintWriter getWriter() {
        if (output != null) throw new IllegalStateException("Stream already in use");
        if (writer == null) {
            writer = new PrintWriter(new OutputStreamWriter(capture, StandardCharsets.UTF_8));
        }
        return writer;
    }

    @Override
    public void flushBuffer() throws IOException {
        if (writer != null) writer.flush();
        if (output != null) output.flush();
    }

    // 캐싱된 응답 바디를 꺼내보는 메서드
    public byte[] getContentAsByteArray() {
        return capture.toByteArray();
    }

    // 최종적으로 클라이언트에게 데이터를 전송하는 메서드 (필수!)
    public void copyBodyToResponse() throws IOException {
        flushBuffer();
        byte[] content = capture.toByteArray();
        ServletOutputStream out = getResponse().getOutputStream();
        out.write(content);
        out.flush();
    }
}

사용법

• Filter에서 사용 예시

java
@Component
public class LoggingFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {

        // mutipart 요청은 래핑하지 않도록 변경
        String contentType = request.getContentType();
        if(contentType != null && contentType.startsWith("multipart/")) {
            filterChain.doFilter(request, response);
            return;
        }

        // 여기서 딱 한 번만 래핑합니다.
        MultiReadRequestWrapper requestWrapper = new MultiReadRequestWrapper(request);
        MultiReadResponseWrapper responseWrapper = new MultiReadResponseWrapper(response);

        try {
            filterChain.doFilter(requestWrapper, responseWrapper);
        } finally {
            logRequestAndResponse(requestWrapper, responseWrapper);
            responseWrapper.copyBodyToResponse();
        }
    }

    private void logRequestAndResponse(MultiReadRequestWrapper request, MultiReadResponseWrapper response) throws IOException {
        String requestBody = new String(request.getContentAsByteArray(), StandardCharsets.UTF_8);
        String responseBody = new String(response.getContentAsByteArray(), StandardCharsets.UTF_8);

        log.info("Request: [{} {}] | Body: {}", request.getMethod(), request.getRequestURI(), requestBody);
        log.info("Response: [Status {}] | Body: {}", response.getStatus(), responseBody);
    }
}